Regadenoson is an A2A adenosine receptor agonist that is a coronary vasodilator. It produces maximal hyperemia quickly and maintains it for an optimal duration that is practical for radionuclide myocardial perfusion imaging.
It was approved by the United States Food Drug Administration on Apr. 10, 2008 and is marketed by Astellas Pharma under the tradename Lexican. It has now gained approval in the European Union and is being sold in both the United Kingdom and Germany.
Regadenoson has a 2- to 3-minute biological half-life, as compared with adenosine's 30-second half-life. Regadenoson stress protocols using a single bolus have been developed, obviating the need for an intravenous line. Regadenoson stress tests are not affected by the presence of beta blockers, as regadenoson vasodilates but do not stimulate beta adrenergic receptors.

The following patents and applications describe the synthesis of Formula I
A class of compounds possessing these desirable properties was disclosed in U.S. Pat. No. 6,403,567, the complete disclosure of which is hereby incorporated by reference. In particular, one compound disclosed in this patent, (1-{9-[(4S,2R,3R,5R)-3,4-dihydroxy-5-(hydroxymethyl)oxolan-2-yl)-6-aminopurin-2-yl}pyrazole-4-yl)-N-methylcarboxamide, has been shown to be a highly selective A2A adenosine receptor agonist, and is presently undergoing clinical trials as a coronary vasodilator useful in cardiac imaging.
WO2008/143667 A1 provides the convenient synthesis for the large scale preparation of (1-{9-[(4S,2R,3R,5R)-3,4-dihydroxy-5-(hydroxymethyl)oxolan-2-yl)-6-aminopurin-2-yl}pyrazole-4-yl)-N-methylcarboxamide, and polymorphs thereof, preferably as its monohydrate. Accordingly, in a first aspect, the invention relates to the preparation of a formula I.
Given the heightened interests in this compound, it has become desirable to find new methods of synthesis that provide a convenient method for making large quantities of the material in good yield and high purity. The patent (U.S. Pat. No. 6,403,567) provides several methods for preparing the compound. Although these methods are suitable for small scale syntheses, all synthetic methods disclosed in the patent utilize protecting groups, which is undesirable for large scale synthesis.
A novel process for preparation of Regadenoson has also been disclosed in applicant's Indian Patent Application No. 4486/CHE/2012 and the corresponding PCT application No. PCT/IN2013/000654 which is incorporated herein by reference.
U.S. Pat. No. 8,106,183B2 describes four polymorphs of Regadenoson and reports Regadenoson Monohydrate as a stable polymorph.
W02012149196A1 describes a polymorph Form-D of Regadenoson.
IN 2011MU01470 describes several hydrated forms of Regadenoson and also reports anhydrous form.
Still there is a need for a highly pure form of Regadenoson for preparation of pharmaceutical formulations.